Fast National ratings for Wednesday, April 24, 2013The first new episodes of "Arrow" and "Supernatural" in three weeks scored ratings gains for The CW Wednesday, with "Supernatural" scoring its second-biggest total audience of the season. NBC's "Law & Order: SVU" also returned from some time off with improved numbers, grabbing its best 18-49 rating since January.Also Wednesday, the Top 4 performances on "American Idol" gave FOX an across-the-board win for the night, although the show was off a tick from last week. "Survivor: Caramoan" tied its season best in the 18-49 demographic. The rest of CBS' lineup and all but one show on ABC were reruns.FOX delivered 12.2 million viewers and a 7.5 rating/12 share among households in primetime. CBS (7.8 million, 4.9/8) finished second, leading third-place NBC (5.6 million, 3.8/6) by a couple million viewers. ABC (4.2 million, 2.8/4) was fourth. The CW came in at 2.7 million viewers and a 1.6/3.FOX also led...